Cellular: Added BG96 handling for socket closing URC

[mirelachirica]

Description

BG96 wasn't handling URC for socket closing at all. Now socket closed flag is set on the arriving of such URC. Also, if the socket was closed but closed flag not yet set at the moment a socket sending/receiving was issued, the socket would get stuck waiting for data. To prevent this, socket event is called also when socket close URC arrives.

Pull request type

[ x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[ciarmcom]

@mirelachirica, thank you for your changes.
@ARMmbed/mbed-os-wan @ARMmbed/mbed-os-maintainers please review.

[blind-owl]

Change request to:
nsapi_error_t SIMCom_SIM7020_CellularStack::socket_close_impl(....) function

Start function with:
CellularSocket *sock = find_socket(sock_id);
MBED_ASSERT(sock != NULL);
if (sock->closed) {
return NSAPI_ERROR_OK;
}

Justification:
When working other modem driver implementation it was discovered during R&D that if one:

• closes a socket within the modem , which is already closed it returns an error

Also it makes more sense, as closed flag is enforced, not to issue close to a modem as there is no need => performance optimization

[mbed-ci]

Test run: FAILED

Summary: 5 of 7 test jobs failed
Build number : 2
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_mbed2-build-ARM
• jenkins-ci/mbed-os-ci_build-IAR
• jenkins-ci/mbed-os-ci_mbed2-build-GCC_ARM
• jenkins-ci/mbed-os-ci_build-ARM
• jenkins-ci/mbed-os-ci_mbed2-build-IAR

[0xc0170]

Aborted build, we need CI time for 5.12.2 jobs today

[mirelachirica]

Change request to:
nsapi_error_t SIMCom_SIM7020_CellularStack::socket_close_impl(....) function

Start function with:
CellularSocket *sock = find_socket(sock_id);
MBED_ASSERT(sock != NULL);
if (sock->closed) {
return NSAPI_ERROR_OK;
}

Justification:
When working other modem driver implementation it was discovered during R&D that if one:

• closes a socket within the modem , which is already closed it returns an error

Also it makes more sense, as closed flag is enforced, not to issue close to a modem as there is no need => performance optimization

For BG96, closed URC can be followed by AT+QICLOSE command, to close the socket, without error because there is a slight distinction in this case between socket and a connection on that socket. This URC indicates connection being closed.

[mirelachirica]

@blind-owl are the changes made to address your comments ok?

[blind-owl]

@mirelachirica looks ok.

[0xc0170]

Ci started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 3
Build artifacts